1. Field of the Invention
The present invention relates, in the field of the composite materials, to an angle bracket aimed at connecting parts forming an angle between them.
Such an angle bracket made of composite material is essentially, but not restrictively, for use in the field of aeronautics, for example for connecting two or more parts, or for reinforcing an angle, over a determined joining length, and in substitution of similar angle brackets hitherto made of metal. These angle brackets are aimed at being made integral with the parts to be connected, and are thus provided on the outside of the fold with coupling regions aimed at permitting the fastening of said parts to be connected, in association with securing means, which may non-restrictively consist of gluing, riveting or screwing means.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
A state-of-the-art angle bracket is represented in FIG. 1. This angle bracket 1 includes two wings 10 and 11, which form between them a right angle according to a longitudinal folding axis 12, the outer faces 13 and 14 of which form the coupling regions, while a multiplicity of holes 15 arranged in the wings 10 and 11, on both sides of said folding axis 12, are aimed at permitting the fastening of the parts to be connected through securing means.
The substitution of the metallic angle brackets by angle brackets made of composite material is essentially dictated by the necessity of weight saving. Generally, the angle brackets made of composite material are manufactured according to the so-called “black metal” technique, which consists in molding a composite material in the shape and dimensions of the angle brackets made of metal they are aimed at substituting. This has sometimes drawbacks at the level of the strength, even when the composite material being used is advantageously formed of reinforcing fibers embedded in a thermoplastic or thermosetting matrix.
It is indeed known that the weak spot of the composite materials is the matrix, which has a specific strength much lower than that of the fibers. The strength range is for example 20 MPa for the resin and 4000 Mpa for the carbon fiber. Therefore, the failure mode of a part made of composite material is generally a fracture of the resin connecting the fibers, and for an angle bracket made of composite material the fracture is observed essentially during an unfolding operation, i.e. the spreading of the two wings.
In order to cope with this drawback, it would be appropriate that the reinforcing fibers are subjected to the tensile and/or compression forces, and that the resin is not or little stressed.
From WO2010072952 is known an L-shaped fitting resulting from the molding of a composite material, which comprises two portions forming an angle between them, and drilled with holes in order to permit to make two parts integral with each other through fastening means, at least one of said two parts having, on the inside of said fitting, a concave curved profile, and in particular a spherical or cylindrical profile, the hole or holes provided in same having an axis radial to the curvature.
This configuration permits the reinforcing fibers, or part of the latter, to be oriented in the direction of traction and/or compression, so that they are stressed by priority with respect to the resin.
However, such an L-shaped fitting does not permit to substitute an angle bracket for assembling, with the desired rigidity, two parts forming an angle between them. Indeed, though an L-shaped fitting is also aimed at making integral two parts forming an angle between them, an angle bracket permits in addition to perform such a uniting over a determined joining length, whereby said parts may for example consist of panels.
It could be contemplated to juxtapose several of these L-shaped fittings, so as to obtain an aggregate of parts extending over the length of the joining of two parts to be assembled. Though the result achieved, at the level of the resistance to a folding or unfolding stress, i.e. when closing or opening the angle, is obviously better than the one that could be achieved with traditional angle brackets, the same does not apply as regards the strength in the longitudinal direction, parallel to the folding axis. Indeed, the L-shaped fittings of the aggregate are not connected to each other, except by said very parts, which do not necessarily have a high rigidity.